Episode Transcript
Hi and Welcome to Clerkship Ready - Pediatrics - A podcast aimed at helping you excel during your clinical clerkship in Pediatrics.
I am Dr. Rebecca Hu, and I am a Pediatric Resident at the University of Virginia.
Today, we will be reviewing what you need to know before you take care of a child or adolescent with asthma for the first time!
Asthma is a common and chronic disease diagnosed and managed by pediatricians, and the severity of asthma can range from a patient needing an inhaler a few times a year to requiring ICU admission for respiratory distress. The goal of this podcast episode is to help you feel more comfortable with understanding the pathophysiology, diagnosis, triggers, and options for the treatment of asthma across different settings. Of note, there are many other causes of wheezing – you may hear people say “not all that wheezes is asthma,” but we are going to focus on asthma in this episode.
Asthma affects 1 in 12 children aged 0 to 17 in the United States and is a leading cause of emergency department visits, hospitalizations, and missed school days. You will definitely come across patients who have asthma on your Pediatrics rotation, whether it be in the primary care setting, Emergency Department, inpatient service, or pediatric ICU.
The exact cause of asthma is actually still unclear. There is clearly a genetic component, asthma is part of the “atopic triad” of asthma, atopic dermatitis or eczema, and allergic rhinitis that may be a part of either the the child’s personal history or family history, but it is also thought that prenatal and childhood environmental factors such as maternal smoking and allergen exposure also shape the development of asthma.
Let’s talk about the pathophysiology and diagnosis of asthma.
The American Academy of Pediatrics definition of asthma is “episodic and reversible airway constriction and inflammation in response to infection, environmental allergens, and irritants. It is a complex, multifactorial, and immune-mediated process that presents with various clinical phenotypes.”
For example, a child with asthma may get a viral upper respiratory illness over the winter, then the pathogen will move into their lower respiratory tract. Because the asthma causes airway hyperreactivity, even if the pathogen doesn’t cause infection in the lower respiratory tract, this triggers multiple pathways of inflammation that ultimately lead to the different components of asthma: inflammation or swelling of the bronchi, increased mucus production, and bronchial smooth muscle contraction. Together, these create an obstructive process and the classic symptoms of cough, wheeze, and shortness of breath.
The diagnosis of asthma is usually clinical and does not necessarily require referral to a pulmonologist or formal pulmonary function testing. One example of a classic history would be a 5-year-old with eczema and allergic rhinitis who wheezes and coughs every time they get a cold, especially at night, and their work of breathing improves when their mom gives them their sibling’s albuterol inhaler.
This example gets at three key elements of the history – recurrent episodes of cough, wheeze, or difficulty breathing, nighttime symptoms, and a consistent trigger. There are a few bonus facts too, including an atopic personal and family history and improvement with asthma treatment.
If the diagnosis is unclear based on history alone or there are confounding factors, auscultating before and after a bronchodilator for improved air movement may be helpful, as well as referring to a pediatric pulmonologist. We will discuss bronchodilators in more detail shortly. A pediatric pulmonologist can perform spirometry, or a type of pulmonary function test that measures the ratio of the FEV1 to FVC, or the forced expiratory volume in 1 second to the forced vital capacity. If this ratio is low, which suggests an obstructive process, and improves after a bronchodilator, then asthma is a likely diagnosis.
It is important to identify a child’s asthma triggers so that they can reduce exposure to these triggers and/or be prepared for potential asthma exacerbations after being exposed to one of their triggers. Common triggers include respiratory infections, mold or pet dander, pollen, intense crying or laughing, exercise, pollution, and cold air. Children from minority and lower-income backgrounds experience an increased asthma burden, likely closely tied to a complex interaction of factors such as decreased access to healthcare, increased rates of obesity, and poor air quality in the areas in which they live.
The type or classification of asthma for a child is determined by the frequency and severity of their symptoms, it ranges from mild intermittent, which means that the child has mild symptoms, such as episodes of wheeze with activity or nighttime cough, less than once or twice a week, and they are fine in-between episodes with no functional impairment - to severe persistent, which means that they have symptoms every day multiple times a day, nightly awakenings, frequent albuterol use, and significant functional impairment. Note that the classification of asthma is based on the child’s symptoms when they are not receiving preventative treatment.
Obviously, the treatment of each patient with asthma is very different, depending on the severity of their asthma. There have been some very exciting new developments in the last few years, with new guidelines that were released in 2022 from the Global Initiative for Asthma that resulted in major changes in practice recommendations. I will put the link to these guidelines in the Show Notes.
In the primary care setting, we often prescribe albuterol as needed for children with mild intermittent asthma who cough or wheeze with allergies or infections a few times a year but are otherwise asymptomatic. If they have symptoms multiple days a week, we will recommend a daily controller medication, usually an inhaled corticosteroid, to prevent symptoms. A general rule of thumb is that if you have symptoms more than twice a week or need to use your albuterol inhaler more than twice a week, you need intensification of your asthma treatment plan.
How do albuterol and inhaled corticosteroids work to control asthma symptoms?
Albuterol is a beta 2 agonist that relaxes bronchial smooth muscles, which leads to symptomatic improvement within minutes. However, albuterol also has some cross reactivity with beta 1 receptors in the heart, so patients will often have tachycardia and it can also make some children more hyperactive or jittery. Note that albuterol is a short acting beta 2 agonist effective for up to a few hours. There are long-acting beta 2 agonists that work for an entire day, such as salmeterol and formoterol.
While the beta agonist is relaxing the bronchial smooth muscles, inhaled corticosteroids work to decrease the underlying inflammation that is also driving the smooth muscle hyperreactivity. Inhaled corticosteroids such as budesonide and fluticasone, brand names Pulmicort and Flovent respectively, can be used alone or in combination with long-acting beta agonists, with brand names such as Advair (which fluticasone and salmeterol) or Symbicort (which is budesonide and formoterol).
There is no one-fits-all approach to picking the exact medication for a patient. Traditionally, many patients have been treated with a daily inhaled corticosteroid, plus albuterol as needed for symptoms. The 2022 guidelines recommend using a single inhaler that contains both an inhaled corticosteroid and long-acting beta agonist for anyone over 5 years of age. This new approach is helpful in that the patient and family only have to think about 1 medication to use in any situation. Additionally, use of a combined inhaled corticosteroid and long-acting beta agonist compared to use of short acting beta agonists alone has been shown to significantly reduce severe exacerbations and asthma-related death. The downside of the combined corticosteroid and long-acting beta agonist is that, particularly for the pediatric population, many insurance companies are still not covering the cost of these inhalers or require prior authorizations, which can be difficult to obtain.
In the outpatient setting, we make sure that every patient with asthma has something called an asthma action plan, which tells them what to do when their asthma is well controlled, what to do when an exacerbation is likely – such as when they get an upper respiratory infection, and what to do when they are having an acute exacerbation. We also make sure that they have a spacer, so that the medication is pre-aerosolized in the chamber and effectively delivered into the child’s lungs instead of staying in the child’s mouth. Some children may need more than 1 spacer, so that they can have one both at home and at school, or if they move between more than 1 home. Ask your resident or attending which asthma medications they use for their patients, and how to access the asthma action plan, so that you can help by completing it and discussing it with your patients!
Thus far, we’ve been talking about patients who have asthma, but don’t have symptoms when you see them.
What if they are having symptoms of wheezing or coughing when you see them? You now have a patient who has a chronic disease – asthma – but with an acute presentation – wheezing, coughing, or difficulty breathing. So it is important to think both about how to best treat the acute phase, while also considering if changes to the treatment of the chronic disease is needed.
Depending on how the child appears, you may not be able to go through a leisurely history and physical. You may need to quickly assess them, get your resident or attending if you’re worried that they need treatment quickly – and then get the history once they are stabilized. Important elements of the history include duration and severity of symptoms, response to treatments they have tried, ability to drink fluids to stay hydrated, and interventions for their asthma they have required in the last year. If the patient has required multiple courses of steroids in the last year, this suggests that their asthma is not well controlled. If the child has required admission to the pediatric ICU or required intubation in the past, the chances that they will do so again are higher and raise our overall concern about the patient. On the physical exam of a patient with asthma, the general appearance and cardiopulmonary exams are the most pertinent. For example, a child with less severe asthma symptoms will be alert, playful, able to speak in full sentences, and on lung exam may have some wheezing, but good air movement throughout. On the flip side, a child with more severe asthma symptoms may be sleepy, tired-appearing, only able to speak 1-word sentences and on lung exam may also have some wheezing, but poor air movement throughout. It is also important to assess the degree of their difficulty breathing or work of breathing – rapid respirations, difficulty speaking, or retractions (when you can see the muscles in-between their ribs – intercostal – or in their neck – supraclavicular – going in and out with each breath). If they have increased work of breathing, but you don’t hear any wheezing, don’t assume that they are okay! It may be that their lungs sound clear because they are not moving any air, sometimes you will hear someone describe this patient as “sounding tight.”
In patients with acute asthma symptoms, we will treat the acute presentation first, then address the chronic control of their asthma. Usually, if their asthma symptoms are relatively mild, you can start with albuterol, given either via an inhaler with a spacer or via a nebulizer machine. The dose of albuterol depends on the child’s weight and whether it is given via an inhaler and spacer or nebulizer. It is important to listen to their lungs again after the first treatment to decide if the child needs another treatment, can go home with an asthma action plan, or if they need to go to the Emergency Department for further evaluation and treatment. We will also treat the child with systemic steroids, usually oral, if they are actively wheezing.
Let’s move into the emergency department, where you will frequently see a child with poor air movement, respiratory distress, and potential hypoxemia – all signs and symptoms of an acute asthma exacerbation. The first line of treatment is what we often call stacked duonebs, or 3 back-to-back nebulizer treatments of combined ipratropium and albuterol. Ipratropium is a muscarinic antagonist that blocks the effect of acetylcholine and results in rapid bronchial smooth muscle dilation, in a duoneb, this is combined with the bronchial relaxation caused by albuterol via beta 2 agonism as we discussed earlier. In conjunction with this power combo of immediate bronchodilation, it is important to give systemic– oral, intramuscular, or intravenous – steroids, most commonly dexamethasone or prednisone, to start working on gradually calming down the underlying inflammation.
After giving the stacked duonebs, it is extremely important to reexamine the patient and make sure that their work of breathing and air movement have improved. Sometimes they will actually have much more wheezing due to air moving through the bronchi that were previously completely closed. If they have improved, the child can continue to be monitored to make sure that they do not require a subsequent albuterol treatment sooner than 3-4 hours. If they continue to do well after 3-4 hours and are otherwise well-appearing, the child can be discharged with oral steroids, another 24 hours of scheduled albuterol every 3-4 hours, and close follow-up with their primary care provider.
What if they don’t improve?
If the child starts having increased symptoms and requires albuterol sooner than 3-4 hours after the stacked duonebs, is requiring respiratory support, or is at high risk for persistent exacerbation, admission to the hospital is required.
On the inpatient service, we support children with similar interventions that to the ones they receive in the emergency department, such as steroids and albuterol – and if they are still having severe symptoms, maybe ipratropium – these treatments are gradually spaced out as they improve. If the child has hypoxemia or increased work of breathing, we can also use non-invasive respiratory support such as low or high flow oxygen via nasal cannula. Children on higher levels of respiratory support may also require IV fluids until the level of respiratory support they require is low enough for them to safely drink by mouth without the risk of aspiration.
What if the child comes in in significant respiratory distress and doesn’t improve with the initial stacked duonebs?
This is where we consider continuous inhaled albuterol and other medications such as magnesium, terbutaline, theophylline, and epinephrine that don’t depend on open airways for medication delivery. It is important to call the pediatric ICU for possible admission as well. You always have to remember that the ABCs, airway, breathing, and circulation, are the priority, and if they are in such a severe exacerbation that they are unable to ventilate or have impaired mentation, intubation should be the first line intervention.
Let’s return to talking about 2nd and 3rd line medications, even though we thankfully don’t have to use these medications very frequently, it’s important to know how they work.
Intravenous magnesium has two mechanisms of action. It causes bronchodilation by blocking calcium channels in smooth muscle and also has some anti-inflammatory effects through several mechanisms, which we won’t go into today. IV magnesium is a common second line medication for patients experiencing serious asthma exacerbations.
Terbutaline is a beta 2 agonist similar to albuterol that can be given by inhaled, subcutaneous, or intravenous route. If you’ve done your OB rotation, you may remember that terbutaline relaxes the uterus and may be used to try to delay birth when there is preterm labor.
Theophylline is another bronchodilator that is not commonly used these days, because it has a very narrow therapeutic window. It acts via multiple pathways including as a phosphodiesterase inhibitor and adenosine antagonist.
Epinephrine is both a beta and alpha agonist, with more beta activity at lower doses and more alpha activity at higher doses. So, it also works as a bronchodilator when given at lower doses. Epinephrine can be given through a variety of routes, including intravenously, through the endotracheal tube if the patient is intubated, intramuscularly, or subcutaneously, which is how it is usually used for patients with asthma.
Whew that was a lot.
I hope that today’s podcast episode about the pathophysiology, diagnosis, triggers, and options for the treatment of asthma across different settings has been helpful. While asthma is common disease in pediatrics, the management can be complex and hopefully what you learned today can help you take a deep breath the next time you see a patient with asthma.
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